Reaching unprecedented speeds for human travel at the time, the spacecraft broke free of the Earth's gravitational pull and entered orbit around the planet, circling once before re-entering the atmosphere and landing back on Soviet soil.

Here are six facts about Gagarin's historic mission:

How long was Gagarin up there?

The total mission lasted just 108 minutes, and the trip once around the Earth at 17,500 mph (most of the way) took less than an hour and a half. [Video: The First Human Spaceflight]

In that time, Vostok 1 completed one not-quite-circular orbit, at a maximum altitude of 203 miles, before slowing down to the point that the capsule was pulled back into the atmosphere for ballistic re-entry.

Here the re-entry capsule of the Vostok 3KA-3 (also known as Vostok 1) spacecraft (Vostok 1) is seen with charring and its parachute on the ground after landing south west of Engels, in the Saratov region of southern Russia.Credit: ESA

The Vostok was a spherical capsule, designed to eliminate changes in center of gravity. In that way, the craft could assure comfort for its one-man crew no matter its orientation. What it wasn't designed to do was land with a human still on board.

Unlike later Russian space vehicles, such as the modern Soyuz capsule, Vostok 1 was not outfitted with thrusters to help slow it down as it headed back toward Earth, so Gagarin had to eject before reaching ground, at an altitude of around 4 miles.

But since the achievement would not have been regarded as the first successful manned mission to space unless it included a manned landing, the Russians kept this little detail out of official press releases. [How the First Human Spaceflight Worked]

What prevented earlier missions from reaching orbit?

In a word: speed.

In order to reach Earth orbit at Vostok 1's altitude, a ship needs to hit 17,500 mph, or about 5 miles per second. Before the Vostok 1 mission, no rocket was powerful enough to get a vessel going that fast. The Vostok capsule's cannonball shape helped the rocket and spacecraft reach the necessary velocity.

How did they test the Vostok before Gagarin’s mission?

A few weeks prior, a prototype of Gagarin's craft, the Vostok 3KA-2, completed one low-Earth orbit carrying a life-size dummy named Ivan Ivanovich and a dog called Zvezdochka.

Ivan was sold in a Sotheby's auction in 1993.

Who was Yuri Gagarin?

Yuri Gagarin was a 27-year-old Soviet Air Force pilot when he made his first and only trip into space. Upon his triumphant return he instantly became a national treasure, too valuable to send on such a dangerous mission again.

It's a sad irony, then, that when Gagarin was finally scheduled to ascend to the cosmos once more, he died in a crash during a routine training exercise. Gagarin remained a hero after the fall of the Soviet Union; statues of him were preserved while monuments to Russia's Communist leaders were torn down.

Modern cosmonauts still observe a sacred launch-day tradition based on Gagarin's preflight preparations in 1961. On the way to the launch pad, the bus carrying the crew stops so that the members can hop out and "take a leak," just as Gagarin did the morning he made history.

A Russian Soyuz TMA-21 spacecraft, named for famed cosmonaut Yuri Gagarin - the first human in space - launches from Baikonur Cosmodrome in Kazakhstan on April 4, 2011 at 6:18 p.m. EDT. Credit: NASA TV

One lasting legacy of Gagarin's historic spaceflight is the mission's launch pad at Baikonur Cosmodrome. The launch pad is still in use today – with the latest crew of the International Space Station blasting off from the site last week on April 5 local time (late April 4 EDT).

Baikonur Cosmodrome is one of several launching sites used by Russia's Federal Space Agency (also known as Roscosmos), but it is not in Russia. The launch site is in Kazakhstan, a country that was part of the Soviet Union during the Cold War but is now a separate nation.

Cosmonauts continued launching from Gagarin's Vostok 1 pad throughout the Cold War, and the tradition continues to this day.